This application is related to and claims priority from Japanese Patent Applications No. Hei. 11-41791 filed on Feb. 19, 1999, and No. Hei. 11-309415 filed on Oct. 29, 1999, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a combustion device which is suitably used for a heating unit for heating a passenger compartment of a vehicle or for heating a vehicle component, for example.
2. Description of Related Art
In a conventional combustion device described in JP-A-9-209875, a fuel collision space is provided at a downstream position of an injection nozzle of a fuel injection unit, nozzle holes are provided at positions opposite to the fuel collision space with each other, and fuel injected from the injection nozzle is introduced into the fuel collision space from the nozzle holes to collide with each other in the fuel collision space.
Fuel collided in the collision space is pounded to become a minute-particle atomized state. The atomized fuel spreads from the collision space to a combustion chamber, and thereby improving combustion effect of fuel in the combustion chamber. Because the injection fuel collides with each other in the fuel collision space to be atomized, an ignition time delay during an ignition is prevented.
However, in the conventional combustion device, since the fuel collision space is provided at the downstream side of the injection nozzle, a wall for defining the fuel collision space restricts fuel from flowing from the injection nozzle to the combustion chamber. Therefore, fuel may be not distributed in an entire range in the combustion chamber, and fuel combustion performance during a normal combustion becomes insufficient.
In view of the foregoing problems, it is an object of the present invention to provide a combustion device in which fuel injected from a fuel injection unit is readily introduced into a combustion chamber in a wide range while being sufficiently atomized.
According to the present invention, a combustion device includes a combustion receiver for defining a combustion chamber, a fuel injection unit having an injection port for injecting fuel to be introduced into the combustion chamber, an air supplying unit for supplying air into the combustion chamber, an ignition unit for igniting a mixed gas between fuel and air in the combustion chamber, and a fuel collision unit disposed between the injection port and the combustion chamber. The position of the fuel collision unit is set so that, a part of fuel injected from the injection port of the fuel injection unit collides with the fuel collision unit, and the other part of fuel is directly introduced from the injection port to the combustion chamber while being prevented from colliding with the collision unit. Thus, a part of fuel introduced into the combustion chamber is atomized by the fuel collision. As a result, even when temperature of the combustion chamber is low (e.g., normal temperature) at an ignition time, because the part of fuel is atomized, mixing performance between fuel and air is improved. Therefore, ignition performance of mixed gas is improved, and an ignition delay time is reduced. On the other hand, because the other part of fuel is directly introduced into the combustion chamber without collision, fuel can be introduced into a wide range of the combustion chamber, and combustion performance in the combustion chamber is improved.
Preferably, when fuel injected from the injection port of the fuel injection unit passes through a fuel opening of a plate portion of the fuel collision unit, a part of fuel is introduced into the combustion chamber while colliding with an edge portion between an inner wall defining the fuel opening and a surface of the plate portion at a side of the combustion chamber, and the other part of fuel is introduced into the combustion chamber through the fuel opening while being prevented from colliding with the edge portion. Therefore, distributing performance of fuel in the combustion chamber is further improved, and the fuel atomization is facilitated using a steering force of the edge portion.
More preferably, the combustion device further includes a detecting unit for detecting a combustion state of mixed gas between fuel from the fuel injection unit and air from the air supplying unit, and a control unit for controlling an operation state of the fuel injection unit in accordance with the combustion state detected by the detecting unit. Further, the fuel injection unit includes an electromagnetic valve for injecting liquid fuel having a pressure higher than a predetermined pressure, and the control unit controls a fuel injection frequency of the electromagnetic valve in accordance with the combustion state detected by the detecting unit. Thus, the fuel atomization is further improved in a case such as the ignition time, and the mixing performance between fuel and air is further improved.
According to the present invention, the control unit controls a fuel-collision switching unit to selectively set a collision mode where fuel injected from the fuel injection unit is introduced into the combustion chamber while colliding with a collision member, and a non-collision mode where fuel injected from the fuel injection unit is introduced into the combustion chamber without colliding with the collision member, in accordance with temperature within the combustion chamber. Thus, even when the temperature of the combustion chamber is low, the fuel atomization is improved. On the other hand, when the temperature of the combustion chamber is high, fuel is introduced into the combustion chamber in a wide range, and fuel distribution performance is improved.
On the other hand, the switching between the collision mode and the non-collision mode is performed in accordance with pressure of air supplying from the air supplying unit. Further, the control unit controls the fuel-collision switching unit to set the collision mode when the pressure of air from the air supplying unit is lower than a predetermined pressure, and the control unit controls the fuel-collision switching unit to set the non-collision mode when the pressure of air from the air supplying unit is higher than the predetermined pressure. Thus, combustion performance of fuel in the combustion chamber is further improved.